From ABC News in Science, 2o August 2013:
Researchers have paired up a fungus and a bacteria to produce high-quality biofuel from agricultural waste materials such as corn stalks and leaves.
Using the fungus Trichoderma reesei and the common bacteria Escherichia coli, US researchers were able to produce 1.88 grams of the biofuel isobutanol, per litre of fluid, which represents the highest concentration yet achieved in the conversion of plant material into biofuel.
The results are published this week in the Proceedings of the National Academy of Sciences.
The researchers chose isobutanol as their desired biofuel, rather than the more common ethanol, because isobutanol gives off 82 per cent of the heat energy petrol provides when burned, compared to ethanol’s 67 per cent. Unlike ethanol, isobutanol doesn’t easily absorb water, which can corrode pipelines and damage engines.
They also took the relatively new approach of using two types of microbes rather than one.
“Previously people have tried to engineer one microbial species or strain to do all of these things including biomass degradation and the fermentation for making the fuel molecules, and this has turned out to be really difficult,” says Professor Xiaoxia Nina Lin, assistant professor at the University of Michigan’s chemical engineering department.
“It’s actually not surprising because what you want to do here are very different things so they happen in different organisms naturally but if you want to have them appear in the same organism, it is very hard to engineer.”
In this study, the fungus T. reesei breaks down the tough feedstock into sugars, and the E. coli then converts those into the desired fuel.
However coaxing the two microbes to cooperate is no easy task as co-cultures are notoriously fragile and unstable. Read more.